Every boy should ride "a hobby-horse" of some kind; and whilst play, and plenty of it, must be his daily right in holiday time, he ought not to forget that the cultivation of some branch of the useful Arts and Sciences will afford him a delightful and profitable recreation when [Page 2]satiated with mere _play_, or imprisoned by bad weather, or gloomy with the unamused tediousness of a long winter's evening. The author recollects with pleasure the half-holidays he used to devote to Chemistry, with some other King's College lads, and in spite of terrible pecuniary losses in retorts, bottles, and jars, the most delightful amusement was enjoyed by all who attended and assisted at these juvenile philosophical meetings. It has been well remarked by a clever author, that bees are _geometricians_. The cells are so constructed as, with the least quantity of material, to have the largest sized spaces and the least possible interstices. The mole is a _meteorologist_. The bird called the nine-killer is an _arithmetician_, also the crow, the wild turkey, and some other birds. The torpedo, the ray, and the electric eel are _electricians_. The nautilus is a _navigator_. He raises and lowers his sails, casts and weighs anchor, and performs nautical feats. Whole tribes of birds are _musicians_. The beaver is an _architect_, _builder_, and _wood-cutter_. He cuts down trees and erects houses and dams. The marmot is a _civil engineer_. He does not only build houses, but constructs aqueducts, and drains to keep them dry. The ant maintains a regular _standing army_. Wasps are _paper manufacturers_. Caterpillars are _silk-spinners_. The squirrel is a _ferryman_. With a chip or a piece of bark for a boat, and his tail for a sail, he crosses a stream. Dogs, wolves, jackals, and many others, are _hunters_. The black bear and heron are _fishermen_. The ants are _day-labourers_. The monkey is a _rope dancer_. Shall it, then, be said that any boy possessing the Godlike attributes of Mind and Thought with Freewill can only eat, drink, sleep, and play, and is therefore lower in the scale of usefulness than these poor birds, beasts, fishes, and insects? No! no! Let "Young England" enjoy his manly sports and pastimes, but let him not forget the mental race he has to run with the educated of his own and of other nations; let him nourish the desire for the acquisition of "scientific knowledge," not as a mere school lesson, but as a treasure, a useful ally which may some day help him in a greater or lesser degree to fight "The Battle of Life." [Page 3] THE BOY'S PLAYBOOK OF SCIENCE. CHAPTER I. THE PROPERTIES OF MATTER--IMPENETRABILITY.